Analysis of the working principle of the "HTML PARSER" framework in the Java class library

HTML Parser is a Java library for analysis and operation of HTML documents.Its working principle is to use HTML documents as input, and analyze it as a DOM tree according to the structure of label, attributes and content.During the analysis process, HTML Parser will identify the labels, attributes and text content in the HTML document, build the corresponding node objects, and organize these nodes together through parent -child relationships. HTML Parser provides a series of APIs that can traverse the node of the DOM tree to read and modify the attributes and content of the node, as well as operations such as adding, deleting and mobile nodes.Below is a basic example code, which shows how to use HTML Parser to resolve HTML documents and obtain the node information: import org.htmlparser.Node; import org.htmlparser.Parser; import org.htmlparser.util.NodeList; public class HTMLParserExample { public static void main(String[] args) throws Exception { // Create a Parser object to analyze HTML documents Parser parser = new Parser("http://www.example.com"); // Call the PARSE method parsing HTML document and get the root node of the analysis of the DOM tree Node rootNode = parser.parse(null).elementAt(0); // Traversing all the sub -nodes under the root node and print node information printNodeInfo(rootNode.getChildren()); } private static void printNodeInfo(NodeList nodeList) { if (nodeList != null) { for (int i = 0; i < nodeList.size(); i++) { Node node = nodeList.elementAt(i); // Print the label name and content of the current node String tag = node.getText(); String content = node.toPlainTextString(); System.out.println("Tag: " + tag); System.out.println("Content: " + content); // Recursively Print the sub -node of the current node printNodeInfo(node.getChildren()); } } } } In the above sample code, a Parser object is first created and the URL of the HTML document to be parsed is passed.Then call the PARSE method parsing HTML document and get the root node of the parsing DOM tree.Finally, the method of "Printnodeinfo" by recursively traversing and printing node information can obtain the label and content of all nodes in the HTML document. The working principle of the HTML Parser framework is based on such parsing and node organization mechanisms to analyze HTML documents and provide flexible API operation nodes in order to easily read, modify and process HTML documents.